Slurry, all solid state battery and method for producing all solid state battery

ABSTRACT

A main object of the present disclosure is to provide a slurry capable of forming an all solid state battery with low ion resistivity. The present disclosure achieves the object by providing a slurry comprising a sulfide solid electrolyte and a solvent, and the solvent includes a first solvent and a second solvent, a boiling point of the first solvent is 80° C. or more and less than a crystallization temperature of the sulfide solid electrolyte, the first solvent is acyclic ether based solvent, acyclic ester based solvent, or acyclic ketone based solvent, and a boiling point of the second solvent is the crystallization temperature of the sulfide solid electrolyte or more.

CROSS-REFERENCE TO RELATED APPLICATIONS

This nonprovisional application claims priority to Japanese PatentApplication No. 2019-195270 filed on Oct. 28, 2019, with the JapanPatent Office, the entire contents of which are hereby incorporated byreference.

TECHNICAL FIELD

The present disclosure relates to a slurry, an all solid state batteryand a method for producing an all solid state battery.

BACKGROUND ART

In accordance with a rapid spread of information relevant apparatusesand communication apparatuses such as a personal computer, a videocamera and a portable telephone in recent years, the development of abattery to be used as a power source thereof has been emphasized. Thedevelopment of a high-output and high-capacity battery for an electricautomobile or a hybrid automobile has been advanced also in theautomobile industry. Currently, among various kinds of batteries,lithium ion secondary batteries are attracting attention in terms ofhigh energy density.

Since a liquid electrolyte containing a flammable organic solvent isused for the lithium ion secondary batteries currently available in themarket, installation of a safety device for suppressing temperatureincrease upon short circuit and a structure for inhibiting the shortcircuit are required. In contrast, an all solid state lithium ionsecondary battery, wherein the battery is all solidified by using asolid electrolyte layer instead of the liquid electrolyte, does notinclude the flammable organic solvent in the battery. Therefore, thesimplification of the safety device may be more easily achieved, andthought to be superior in manufacturing cost and productivity.

Patent Literature 1 discloses an all solid state battery produced byusing an electrode composition in a slurry state including a sulfidesolid electrolyte and a polar solvent as a dispersion medium. As thedispersion medium, triethyl amine (tertiary amine), cyclopentyl methylether (ether), etc. are listed.

Patent Literature 2 discloses that a method for producing an all solidstate battery electrode comprises a mixing and kneading step ofproducing an electrode composition in a slurry state by mixing andkneading an active material, a solid electrolyte, a binder and asolvent, a coating step of coating the produced electrode composition ina slurry state, and a drying step of drying the coated electrodecomposition in a slurry state. The solvent includes a good solvent forthe binder and a poor solvent for the binder, and Patent Literature 2discloses to use heptane as the good solvent for the binder and butylbutyrate as the poor solvent for the binder.

Patent Literature 3 discloses that an electrolyte-containing layer isformed in a method for producing an all solid state battery, by using aslurry including a sulfide solid electrolyte, a binder, a ketonesolvent, and a saturated hydrocarbon solvent. Patent Literature 3 alsodiscloses that the ketone solvent remains in the electrolyte-containinglayer. Also, Patent Literature 4 discloses that a composite solidelectrolyte including two kinds of specific solid electrolytes.

CITATION LIST Patent Literatures

-   Patent Literature 1: Japanese Patent Application Laid-Open (JP-A)    No. 2012-212652-   Patent Literature 2: JP-A 2013-118143-   Patent Literature 3: JP-A 2019-091632-   Patent Literature 4: JP-A 2018-170072

SUMMARY OF DISCLOSURE Technical Problem

In Patent Literature 1 and Patent Literature 2, for example, a dryingtreatment for removing the solvent (dispersion medium) is carried outafter the electrode composition in a slurry state is coated. Also,although the electrode layer after drying is pressed, the ionresistivity of the electrode layer tends to be high since the interfaceresistance (friction resistance) between the particles included in theelectrode layer during the press is high. Further, not only theelectrode layer but also when forming a solid electrolyte layer usingthe slurry, the ion resistivity of the solid electrolyte layer tends tobe high.

The present disclosure has been made in view of the above circumstances,and a main object is to provide a slurry capable of forming an all solidstate battery with low ion resistivity.

Solution to Problem

In order to achieve the object, the present disclosure provides a slurrycomprising a sulfide solid electrolyte and a solvent, and the solventincludes a first solvent and a second solvent, a boiling point of thefirst solvent is 80° C. or more and less than a crystallizationtemperature of the sulfide solid electrolyte, the first solvent isacyclic ether based solvent, acyclic ester based solvent, or acyclicketone based solvent, and a boiling point of the second solvent is thecrystallization temperature of the sulfide solid electrolyte or more.

According to the present disclosure, by including the second solventwith the boiling point higher than the first solvent, in addition to aspecific first solvent, a slurry capable of forming an all solid statebattery with low ion resistivity may be obtained.

In the disclosure, the boiling point of the first solvent may be lessthan 200° C.

In the disclosure, the boiling point of the second solvent may be 200°C. or more.

The present disclosure also provides a slurry comprising a sulfide solidelectrolyte and a solvent, and the solvent includes a first solvent anda second solvent, a boiling point of the first solvent is 80° C. or moreand less than 200° C., and the first solvent is acyclic ether basedsolvent, acyclic ester based solvent, or acyclic ketone based solvent,and a boiling point of the second solvent is 200° C. or more.

According to the present disclosure, by including the second solventwith the boiling point higher than the first solvent, in addition to aspecific first solvent, a slurry capable of forming an all solid statebattery with low ion resistivity may be obtained.

In the disclosure, a proportion of the second solvent to 100 weightparts of solid content of the slurry may be 0.05 weight parts or more.

In the disclosure, the slurry may further comprise a binder.

In the disclosure, the slurry may further comprise an active material.

The present disclosure also provides an all solid state batterycomprising a cathode active material layer, a solid electrolyte layer,and an anode active material layer, and at least one layer of thecathode active material layer, the solid electrolyte layer, and theanode active material layer is a solid electrolyte-containing layerincluding a sulfide solid electrolyte, the solid electrolyte-containinglayer includes a first solvent and a second solvent as solvents, aboiling point of the first solvent is 80° C. or more and less than acrystallization temperature of the sulfide solid electrolyte, the firstsolvent is acyclic ether based solvent, acyclic ester based solvent, oracyclic ketone based solvent, a boiling point of the second solvent is acrystallization temperature of the sulfide solid electrolyte or more,and a content proportion of the first solvent in the solidelectrolyte-containing layer is 0.01 weight % or more.

According to the present disclosure, since the solidelectrolyte-containing layer incudes a predetermined amount of aspecific solvent, an all solid state battery with low ion resistivitymay be obtained.

In the disclosure, a content proportion of the second solvent in thesolid electrolyte-containing layer may be 0.05 weight % or more.

In the disclosure, a content proportion of the solvents in the solidelectrolyte-containing layer may be 0.25 weight % or more.

The present disclosure also provides a method for producing an all solidstate battery, the method comprising: a coating step of forming acoating layer by coating a substrate with the above described slurry, adrying step of forming a dried coating layer by drying the coatinglayer, and a pressing step of forming a solid electrolyte-containinglayer by pressing the dried coating layer, and a drying condition in thedrying step is adjusted so as a content proportion of the first solventin the solid electrolyte-containing layer is 0.01 weight % or more.

According to the present disclosure, by adjusting the drying conditionin the drying step so as the solid electrolyte-containing layer includesa predetermined amount of a specific solvent, an all solid state batterywith low ion resistivity may be obtained.

Advantageous Effects of Disclosure

According to the present disclosure, a slurry capable of forming an allsolid state battery with low ion resistivity may be provided.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a schematic cross-sectional view illustrating an example of anall solid state battery in the present disclosure.

FIG. 2 is a flow chart illustrating an example of a part of the methodfor producing an all solid state battery in the present disclosure.

DESCRIPTION OF EMBODIMENTS

A slurry, an all solid state battery, and a method for producing an allsolid state battery in the present disclosure are hereinafter described.Incidentally, the embodiments described below are exemplification, and aslurry, an all solid state battery, and a method for producing an allsolid state battery in the present disclosure are not limited to theembodiments described below.

A. Slurry

The slurry in the present disclosure is a slurry comprising a sulfidesolid electrolyte and a solvent, and the solvent includes a firstsolvent and a second solvent, a boiling point of the first solvent is80° C. or more and less than a crystallization temperature of thesulfide solid electrolyte, the first solvent is acyclic ether basedsolvent, acyclic ester based solvent, or acyclic ketone based solvent,and a boiling point of the second solvent is the crystallizationtemperature of the sulfide solid electrolyte or more.

According to the present disclosure, by including the second solventwith the boiling point higher than the first solvent, in addition to aspecific first solvent, a slurry capable of forming an all solid statebattery with low ion resistivity may be obtained.

Here, when the below described solid electrolyte-containing layer isformed by using a slurry, a coating layer is usually formed by coatingthe slurry, a dried coating layer is formed by drying the obtainedcoating layer, and a solid electrolyte-containing layer is formed bypressing the obtained dried coating layer. Since the slurry in thepresent disclosure includes the second solvent with high boiling pointas a solvent, there is an advantage that the solvent is easily leftremained in the dried coating layer in a positive manner, when thecoating layer is dried. By leaving the solvent remained in a positivemanner, the interface resistance (friction resistance) between theparticles included in the dried coating layer may be reduced during thepressing. In other words, the sliding property between the particlesincluded in the dried coating layer may be improved. Thereby, a denselayer may be formed, and an all solid state battery with low ionresistivity may be obtained.

A solvent with high boiling point as the second solvent is usually notused for a slurry since the evaporation rate at drying is low. A solventwith high evaporation rate at drying, in other words, a solvent with lowboiling point is usually used for a slurry, in light of themanufacturing efficiency. In contrast to this, in embodiments of thepresent disclosure, a suitable manufacturing efficiency may bemaintained by using the first solvent with low boiling point, whereas aslurry wherein the solvent is easily left remained in the dried coatinglayer in a positive manner, may be obtained by using the second solventwith the boiling point higher than the first solvent.

As described above, in Patent Literatures 1 and 2, for example, aftercoating the electrode composition in a slurry state, a drying treatmentis carried out to remove the solvent (dispersion medium). Since thesolvent included in the electrode composition in a slurry state does notusually contribute to the ion conductivity, the solvent is completelyremoved by sufficiently drying. Therefore, Patent Literatures 1 and 2neither describe nor suggest to leave the solvent remained in a positivemanner. Meanwhile, Patent Literature 3 describes that ketone solvent isleft remained in the electrolyte-containing layer. However, PatentLiterature 3 suggests the possibility of a side reaction due to theremained solvent amount, and Patent Literature 3 neither describe norsuggests to leave the solvent remained in a positive manner.

1. Solvent

The slurry in the present disclosure includes a solvent. The solvent inthe present disclosure refers to a solvent in a broad sense, and what iscalled a dispersion medium is included. Also, the solvent in the presentdisclosure includes a first solvent and a second solvent.

(1) First Solvent

The boiling point of the first solvent in the present disclosure is 80°C. or more and less than a crystallization temperature of the sulfidesolid electrolyte, and the first solvent is acyclic ether based solvent,acyclic ester based solvent, or acyclic ketone based solvent.

The boiling point of the first solvent in the present disclosure isusually 80° C. or more. When the boiling point of the first solvent istoo low, the evaporation rate of the first solvent is high so that thesolid content of the slurry is easily agglutinated. The boiling point ofthe first solvent may be 90° C. or more, and may be 100° C. or more.

The boiling point of the first solvent is usually less than thecrystallization temperature of the sulfide solid electrolyte. When theboiling point of the first solvent is the crystallization temperature ofthe sulfide solid electrolyte or more, the sulfide solid electrolytewill be exposed to high temperature for a long time, in order to removethe first solvent. As the result, not only the operational efficiency isdeteriorated, but also the sulfide solid electrolyte is possiblydeteriorated. The boiling point of the first solvent may be lower thanthe crystallization temperature of the sulfide solid electrolyte by 5°C. or more, may be lower by 10° C. or more, and may be lower by 20° C.or more. The boiling point of the first solvent is, for example, lessthan 200° C., may be 170° C. or less, and may be 130° C. or less.

The molecular weight of the first solvent is, for example, 80 or more,and may be 100 or more. Meanwhile, the molecular weight of the firstsolvent is, for example, 150 or less. Also, the viscosity of the firstsolvent at 25° C. is, for example, 0.1 mPa·s or more and 2 mPa·s orless.

Also, the first solvent is acyclic ether based solvent, acyclic esterbased solvent, or acyclic ketone based solvent. The first solvent may bea solvent of one kind, and may be solvents of two kinds or more. Also,the acyclic ether based solvent refers to a solvent whose ether group(—O—) does not constitute a ring structure such as an aromatic ring.Since the ether group of tetrahydrofuran, for example, constitutes aring structure such as an aromatic ring, it corresponds to a cyclicether based solvent. Similarly, the acyclic ester based solvent and theacyclic ketone based solvent refer to solvents whose ester group(—CO—O—) and ketone group (—CO—) do not constitute a ring structure suchas an aromatic ring, respectively.

Since the reactivity of the lone-pair electrons in an oxygen element ishigh, the cyclic ether based solvent such as tetrahydrofuran is likelyto be reacted with the sulfide solid electrolyte. In contrast to this,the acyclic ether based solvent is not likely to be reacted with thesulfide solid electrolyte since the reactivity of the lone-pairelectrons in an oxygen element is low. Similarly, the acyclic esterbased solvent and the acyclic ketone based solvent are not likely to bereacted with the sulfide solid electrolyte.

The acyclic ether based solvent is not likely to be reacted with thesulfide solid electrolyte since it includes an oxygen atom with lowreactivity. In embodiments, the ether based solvent may be, for example,represented by R¹—O—R² (R¹ and R² are independently a hydrocarbon groupor an ether group with carbon number of 2 or more and 6 or less,respectively). Examples of the ether based solvent may includediethylene glycol diethyl ether, cyclopentyl methyl ether, dibutylether, dipentyl ether, and anisole.

Similar to the acyclic ether based solvent, the acyclic ester basedsolvent is not likely to be reacted with the sulfide solid electrolytealso, since it includes an oxygen atom with low reactivity. Inembodiments, the acyclic ester based solvent may be, for example,represented by R³—CO—O—R⁴ (R³ and R⁴ are independently a hydrocarbongroup with contained carbon number of 2 or more and 4 or less,respectively). Examples of the acyclic ester based solvent may includeethyl butyrate, butyl butyrate, and 2-methyl butyl butyrate.

The acyclic ketone based solvent is not likely to be reacted with thesulfide solid electrolyte because of relatively low polarity. Inembodiments, the acyclic ketone based solvent may be, for example,represented by R⁵—CO—R⁶ (R⁵ and R⁶ are independently a hydrocarbon groupwith included carbon number of 2 or more and 4 or less, respectively).Examples of the acyclic ketone based solvent may include methyl ethylketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone,dibutyl ketone, and diisobutyl ketone.

Also, when a saturated hydrocarbon based solvent is used, for example,the solid content (particularly sulfide solid electrolyte) havingpolarity is agglutinated so that the dispersibility is lowered, sincethe polarity of the saturated hydrocarbon based solvent is low. Thereby,the interface resistance is increased, and the ion resistivity may behigher. In contrast to this, the acyclic ether based solvent, theacyclic ester based solvent, and the acyclic ketone based solvent areable to prevent the agglutination of the solid content because of thehigher polarity than the saturated hydrocarbon based solvent.

(2) Second Solvent

The boiling point of the second solvent in the present disclosure isusually the crystallization temperature of the sulfide solid electrolyteor more. Since the boiling point of the second solvent is thecrystallization temperature of the sulfide solid electrolyte or more, aslurry wherein the solvent is easily left remained in the dried coatinglayer in a positive manner, may be obtained.

When the first solvent is left remained in the dried coating layer byusing only the above described first solvent as the solvent of theslurry, for example, since the evaporation rate of the first solvent ishigh, the adjustment of the remaining solvent amount may be difficult,and the solid content of the slurry may be easily agglutinated.Meanwhile, when the second solvent is left remained in the dried coatinglayer by using only the above described second solvent as the solvent ofthe slurry, for example, since the evaporation rate of the secondsolvent is low, the sulfide solid electrolyte will be exposed to hightemperature for a long time, in order to remove the second solvent. Asthe result, not only the operational efficiency is deteriorated, butalso the sulfide solid electrolyte may be deteriorated. In contrast tothis, in embodiments of the present disclosure, a suitable manufacturingefficiency may be maintained by using the first solvent with low boilingpoint. Furthermore, a slurry wherein the solvent is easily left remainedin the dried coating layer in a positive manner, may be obtained byusing the second solvent with the boiling point higher than the firstsolvent.

The boiling point of the second solvent may be higher than thecrystallization temperature of the sulfide solid electrolyte by 5° C. ormore, may be higher by 10° C. or more, and may be higher by 20° C. ormore. The boiling point of the second solvent is, for example, 200° C.or more, may be 220° C. or more, and may be 240° C. or more. Meanwhile,the boiling point of the second solvent is, for example, 350° C. orless. The difference between the boiling points of the second solventand the first solvent is, for example, 40° C. or more, may be 60° C. ormore, and may be 80° C. or more.

In embodiments, the molecular weight of the second solvent may be largerthan the molecular weight of the first solvent. The molecular weight ofthe second solvent is, for example, 120 or more, may be 160 or more, andmay be 200 or more. Generally, as the molecular weight increases, theboiling point of the solvent is higher. Also, as the molecular weightincreases, the reactivity between the solvent and the sulfide solidelectrolyte is decreased. In embodiments, the viscosity of the secondsolvent may be higher than the viscosity of the first solvent. Also, theviscosity of the second solvent at 25° C. is, for example, 1 mPa·s ormore, may be 5 mPa·s or more, and may be 10 mPa·s or more. Generally, asthe molecular weight increases, the viscosity tends to be increased.

Examples of the second solvent may include a ketone based solvent,glycol ether based solvent, ester based solvent, fatty acid ester basedsolvent, hydrocarbon based solvent, alcohol based solvent, sulfoxidebased solvent, sulfone based solvent, amine based solvent, amide basedsolvent, oil based solvent, anion based surfactant, and non-ion basedsurfactant. The second solvent may be a solvent of one kind, and may besolvents of two kinds or more.

Examples of the ketone based solvent may include acetophenone,isophorone, and phorone. Example of the glycol ether based solvent mayinclude triethylene glycol monomethyl ether, and decaethylene glycolmonomethyl ether. Example of the ester based solvent may include3-hydroxy-2,2,4-trimethylpentyl isobutyrate, benzyl acetate, isopentylbutyrate, γ-butyrolactone, and butyl lactate. Examples of the fatty acidester based solvent may include polyethylene glycol monolaurate.

Examples of the hydrocarbon based solvent may include n-dodecane,tetralin, and decahydronaphthalene. Examples of the alcohol basedsolvent may include 1-nonanol, and 2-ethyl-1-hexanol. Examples of thesulfoxide based solvent may include dimethylsulfoxide. Examples of thesulfone based solvent may include sulfolane. Examples of the amine basedsolvent may include o-toluidine, m-toluidine, and p-toluidine. Examplesof the amide based solvent may include N,N-dimethylacetamide, andN-methyl-2-pyrrolidone. Examples of the oil based solvent may includeparaffin, mineral oil, castor oil, tetralin, glycerin, and ethyleneglycol. Examples of the anion based surfactant may include lithiumalkylsulfate, lithium salt of fatty acid, lithium sterate, lithiumpolyacrylate, and styrene-lithium maleate anhydride copolymer.

(3) Solvent

The slurry in the present disclosure includes a first solvent and asecond solvent as the solvent. The total proportion of the first solventand the second solvent to all the solvents in the slurry is, forexample, 70 weight % or more, may be 80 weight % or more, may be 90weight % or more, and may be 100 weight %.

Also, the boiling point of the second solvent is higher than the firstsolvent, and is a solvent left remained in, for example, the laterdescribed solid electrolyte-containing layer in a positive manner. Whenthe solid content of the slurry is regarded as 100 weight parts, theproportion of the second solvent is, for example, 0.05 weight parts ormore, may be 0.1 weight parts or more, and may be 0.3 weight parts ormore. Meanwhile the proportion of the second solvent is, for example, 8weight parts or less, may be 6 weight parts or less, and may be 4 weightparts or less.

Also, the proportion of the second solvent to the total of the firstsolvent and the second solvent in the slurry is, for example, 30 weight% or less, may be 15 weight % or less, and may be 5 weight % or less.Meanwhile, the proportion of the second solvent is, for example, 0.1weight % or more.

The solvent in the present disclosure may or may not include a lithiumsalt. Examples of the lithium salt may include inorganic lithium saltssuch as LiPF₆, LiBF₄, LiClO₄, LiAsF₆, and LiSbF₆; and organic lithiumsalts such as LiCF₃SO₃, LiC₄F₉SO₃, Li[N(FSO₂)₂], Li[N(CF₃SO₂)₂], andLi[C(CF₃SO₂]₃]. The concentration of the lithium salt in the solvent is,for example, 0.5 mol/l or more and 2 mol/l or less.

In the slurry, the solvent and the sulfide solid electrolyte do notusually react with each other. “The solvent and the sulfide solidelectrolyte do not react with each other” means that, when the followingtwo states are compared, the decreasing rate of the ion conductivity ofthe sulfide solid electrolyte is 10% or less; a state before the sulfidesolid electrolyte is immersed in the solvent, and a state after thesulfide solid electrolyte is immersed in the solvent for 1 hour and thendried. The decreasing rate of the ion conductivity of the sulfide solidelectrolyte may be 5% or less, may be 3% or less, and may be 1% or less.

2. Sulfide Solid Electrolyte

The sulfide solid electrolyte in the present disclosure is a materialincluding sulfur (S) and having ion conductivity. The crystallizationtemperature of the sulfide solid electrolyte is, for example, 160° C. ormore, may be 170° C. or more, and may be 180° C. or more. Meanwhile thecrystallization temperature of the sulfide solid electrolyte is, forexample, 240° C. or less, may be 230° C. or less, may be 220° C. orless, and may be 210° C. or less. The crystallization temperature may bedetermined by a differential thermal analysis (DTA).

In embodiments, the sulfide solid electrolyte may contain Li, A (A is atleast one kind of P, Si, Ge, Al, and B) and S. Among them, the sulfidesolid electrolyte may include an anion structure of an ortho composition(PS₄ ³⁻ structure, SiS₄ ⁴⁻ structure, GeS₄ ⁴⁻ structure, AlS₃ ³⁻structure, and BS₃ ³⁻ structure) as the main component of the anion. Inembodiments, the proportion of the anion structure of an orthocomposition with respect to all the anion structures in the sulfidesolid electrolyte may be 70 mol % or more, or even 90 mol % or more. Theproportion of the anion structure of an ortho composition may bedetermined by methods such as a Raman spectroscopy, NMR, and XPS.Further, the sulfide solid electrolyte may further include X (X is atleast one of I, Br and Cl). Also, in the sulfide solid electrolyte, apart of S may be substituted by O.

The sulfide solid electrolyte may be a sulfide glass, and may be asulfide glass ceramic obtained by heat treating the sulfide glass. Thesulfide glass may be obtained by amorphizing a raw material compositionincluding raw material such as Li₂S and P₂S₅, for example. Examples of amethod for amorphizing may include mechanical milling and amelt-quenching method. The reason therefor is to enable the treatment atambient temperature so as to facilitate simplification of themanufacturing process. The mechanical milling is not particularlylimited as long as it is a method mixing the raw material compositionwhile applying mechanical energy, and examples may include a ballmilling, a turbo milling, a mechano-fusion, and a disk milling.

Meanwhile, the sulfide glass ceramic may be obtained by, for example,heat treating the sulfide glass at a temperature of the crystallizationtemperature or more. That is, the sulfide glass ceramic may be obtainedby amorphizing the raw material composition, and further, heat treating.Incidentally, when the sulfide solid electrolyte is the sulfide glassceramic, the crystallization temperature of the sulfide solidelectrolyte means the temperature at which the sulfide glass iscrystallized.

3. Slurry

The slurry in the present disclosure includes a sulfide solidelectrolyte and a solvent. Also, in embodiments, the slurry in thepresent disclosure may be used to produce a cathode active materiallayer, a solid electrolyte layer or an anode active material layer in anall solid state battery. Therefore, in embodiments, the slurry in thepresent disclosure may further include materials such as an activematerial, a conductive material, and a binder, in accordance with theintended layer. These materials are described later.

The solid content concentration of the slurry is not particularlylimited, and is, for example, 30 weight % or more, may be 40 weight % ormore, and may be 50 weight % or more. When the solid contentconcentration of the slurry is too low, the solvent amount is relativelyhigh so that the productivity tends to be decreased. Meanwhile, when thesolid content concentration of the slurry is, for example, 90 weight %or less. When the solid content concentration of the slurry is too high,the viscosity is relatively high so that the coating property tends tobe decreased.

Examples of the method for producing the slurry in the presentdisclosure may include a method wherein the first solvent, the secondsolvent, and the sulfide solid electrolyte are mixed and kneaded.Examples of the mixing and kneading method may include a method usingcommon mixing and kneading devices, such as a dissolver, a homo mixer, akneader, a roll mill, a sand mill, an attritor, a ball mill, a vibratormill, a high speed impeller mill, an ultrasonic homogenizer, and ashaker.

The present disclosure may also provide a slurry comprising a sulfidesolid electrolyte and a solvent, and the solvent includes a firstsolvent and a second solvent, a boiling point of the first solvent is80° C. or more and less than 200° C., and the first solvent is acyclicether based solvent, acyclic ester based solvent, or acyclic ketonebased solvent, and a boiling point of the second solvent 200° C. ormore. That is, “a solvent with boiling point of 80° C. or more and lessthan 200° C.” may be used as the first solvent instead of “a solventwith boiling point of 80° C. or more and less than the crystallizationtemperature of the sulfide solid electrolyte”. Similarly, “a solventwith boiling point of 200° C. or more” may be used as the second solventinstead of “a solvent with boiling point of the crystallizationtemperature of the sulfide solid electrolyte or more”. These points aresimilar for the later described all solid state battery and the methodfor producing the same, not only for the slurry. Also, the details forthe first solvent and the second solvent are described above.

B. All Solid State Battery

FIG. 1 is a schematic cross-sectional view illustrating an example of anall solid state battery in the present disclosure. As shown in FIG. 1,all solid state battery 10 comprises cathode active material layer 1,anode active material layer 2, and solid electrolyte layer 3 formedbetween cathode active material layer 1 and anode active material layer2. An ion is conducted between cathode active material layer 1 and anodeactive material layer 2 via solid electrolyte layer 3.

In all solid state battery 10, at least one layer of cathode activematerial layer 1, anode active material layer 2 and solid electrolytelayer 3 is a solid electrolyte-containing layer including a sulfidesolid electrolyte. This solid electrolyte-containing layer includes afirst solvent and a second solvent as solvents. Further, the contentproportion of the first solvent in the solid electrolyte-containinglayer is usually 0.01 weight % or more.

According to the present disclosure, since the solidelectrolyte-containing layer incudes a predetermined amount of aspecific solvent, an all solid state battery with low ion resistivitymay be obtained.

1. Solid Electrolyte-Containing Layer

The solid electrolyte-containing layer includes a sulfide solidelectrolyte. Further, the solid electrolyte-containing layer includes afirst solvent and a second solvent as solvents. The details for thesulfide solid electrolyte, the first solvent, and the second solvent maybe in the same contents as those described in “A. Slurry” above; thus,the descriptions herein are omitted. Also, the solidelectrolyte-containing layer may be prepared by using the abovedescribed slurry.

The content proportion of the first solvent in the solidelectrolyte-containing layer is usually 0.01 weight % or more, may be0.05 weight % or more, may be 0.1 weight % or more, and may be 0.2weight % or more. Meanwhile, the content proportion of the first solventin the solid electrolyte-containing layer is, for example, 5 weight % orless, may be 3 weight % or less, and may be 1 weight % or less.

The content proportion of the second solvent in the solidelectrolyte-containing layer may be less than the content proportion ofthe first solvent, may be same as the content proportion of the firstsolvent, and may be more than the content proportion of the firstsolvent. The content proportion of the second solvent in the solidelectrolyte-containing layer is, for example, 0.05 weight % or more, maybe 0.1 weight % or more, and may be 0.3 weight % or more. Meanwhile, thecontent proportion of the second solvent in the solidelectrolyte-containing layer is, for example, 8 weight % or less, may be6 weight % or less, and may be 4 weight % or less.

The total proportion of the first solvent and the second solvent to allthe solvent in the solid electrolyte-containing layer is, for example,70 weight % or more, may be 80 weight % or more, may be 90 weight % ormore, and may be 100 weight %.

The content proportion of the solvents (all solvent) in the solidelectrolyte-containing layer is, for example, 0.05 weight % or more, maybe 0.15 weight % or more, and may be 0.25 weight % or more. When thecontent proportion of the solvents is too low, the ion resistivityreducing effect may not be obtained. Meanwhile, the content proportionof the solvents (all solvent) in the solid electrolyte-containing layeris, for example, 10 weight % or less, may be 8 weight % or less, may be6 weight % or less, may be 4.2 weight % or less and may be 3.1 weight %or less. When the content proportion of the solvents is too high, thereis a possibility that the ion conductive inhibiting effect due to thesolvents is larger than the ion resistivity reducing effect due to thesolvents.

The filling rate of the solid electrolyte-containing layer is, forexample, 96% or more, may be 97% or more, and may be 98% or more. Thefilling rate may be determined by the following method. First, theapparent density of the solid electrolyte-containing layer is calculatedfrom area, thickness and mass of the solid electrolyte-containing layer(apparent density of a solid electrolyte-containinglayer=mass/(thickness×area)). Next, the true density of the solidelectrolyte-containing layer is calculated from the true density andcontent of the constituting components of the solidelectrolyte-containing layer (true density of a solidelectrolyte-containing layer=mass/Σ(content of each constitutingcomponent/true density of each constituting component)). The proportionof the apparent density to the true density is regarded as filling rate(%).

The solid electrolyte-containing layer at least include the sulfidesolid electrolyte and the solvent. Also, when the solidelectrolyte-containing layer is an electrode layer, the solidelectrolyte-containing layer includes an active material. The activematerial and other materials will be described later.

2. Cathode Active Material Layer

The cathode active material layer includes at least a cathode activematerial, and may further include at least one of a solid electrolyte, aconductive material and a binder as an optional component. Also, thecathode active material layer in the present disclosure may or may notbe the above described solid electrolyte-containing layer.

Examples of the cathode active material may include an oxide activematerial. Examples of the oxide active material may include rock saltbed type active materials such as LiCoO₂, LiMnO₂, LiNiO₂, LiVO₂,LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂; spinel type active materials such asLiMn₂O₄, and LiNi_(0.5)Mn_(1.5)O₄; and olivine type active materialssuch as LiFePO₄, and LiMnPO₄. Examples of the shape of the cathodeactive material may include a granular shape. The cathode activematerial may be coated with a lithium ion conductive oxide such asLiNbO₃.

Examples of the solid electrolyte may include the above describedsulfide solid electrolyte. Also, examples of the conductive material mayinclude a carbon material and a metal material. Examples of the carbonmaterial may include particulate carbon materials such as acetyleneblack (AB) and Ketjen black (KB); fibrous carbon materials such as VGCF,carbon nanotube (CNT), and carbon nanofiber (CNF). Examples of the metalmaterial may include Ni, Cu, Fe, and SUS. In embodiments, the metalmaterial may be a granular shape or a fibrous shape.

Examples of the binder may include rubber based binders such asbutadiene rubber, hydrogenated butadiene rubber, styrene-butadienerubber (SBR), hydrogenated styrene-butadiene rubber, nitrile butadienerubber, hydrogenated nitrile butadiene rubber, and ethylene-propylenerubber; fluorine based binders such as polyvinylidene fluoride (PVDF),polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP),polytetrafluoroethylene, and fluororubber; polyolefin basedthermoplastic resins such as polyethylene, polypropylene, andpolystyrene; and imide based resins such as polyimide, andpolyamidimide; amide based resins such as polyamide; acryl based resinssuch as polymethyl acrylate and polyethyl acrylate; and methacryl basedresins such as polymethyl methacrylate and polyethyl methacrylate.

3. Anode Active Material Layer

The anode active material layer includes at least an anode activematerial, and may further include at least one kind of a solidelectrolyte, a conductive material and a binder as an optionalcomponent. Also, the anode active material layer in the presentdisclosure may or may not be the above described solidelectrolyte-containing layer.

Examples of the anode active material may include a metal activematerial, a carbon active material, and an oxide active material.Examples of the metal active material may include a metal simplesubstance such as Si, Sn, In, and Al, and an alloy including at leastone kind of these. Examples of the carbon active material may includemesocarbon microbead (MCMB), highly oriented pyrolytic graphite (HOPG),hard carbon, and soft carbon. Examples of the oxide active material mayinclude Nb₂O₅, Li₄Ti₅O₁₂, and SiO. Examples of the shape of the anodeactive material may include a granular shape. For the solid electrolyte,the conductive material, and the binder, similar materials described in“2. Cathode active material layer” above may be used; thus, thedescriptions herein are omitted.

4. Solid Electrolyte Layer

The solid electrolyte layer is a layer formed between the cathode activematerial layer and the anode active material layer. The solidelectrolyte layer includes at least a solid electrolyte, and may furtherinclude a binder as an optional component. Also, the solid electrolytelayer in the present disclosure may or may not be the above describedsolid electrolyte-containing layer. For the solid electrolyte and thebinder, similar materials described in “2. Cathode active materiallayer” above may be used; thus, the descriptions herein are omitted.

5. All Solid State Battery

In embodiments, the all solid state battery in the present disclosuremay include an anode current collector and a cathode current collector,in addition to the cathode active material layer, the solid electrolytelayer, and the anode active material layer. Examples of the materialsfor the anode current collector may include SUS, Cu, Ni, Fe, Ti, Co, andZn. Meanwhile, examples of the materials for the cathode currentcollector may include Cr, Au, Pt, Al, Fe, Ti, and Zn. Also, the allsolid state battery may include an arbitrary battery case such as abattery case made from SUS, for example.

In embodiments, the all solid state battery in the present disclosuremay be an all solid state lithium ion battery. Also, the all solid statebattery may be a primary battery, and may be a secondary battery. Inembodiments, the all solid state battery in the present disclosure maybe the secondary battery, so as to be repeatedly charged and discharged,and is useful as, for example, a car-mounted battery. Examples of theshape of the all solid state battery may include a coin shape, alaminate shape, a cylindrical shape, and a square shape.

Further, the present disclosure may also provide a solidelectrolyte-containing layer used for an all solid state battery, thesolid electrolyte-containing layer including a sulfide solid electrolyteand a solvent, the solvent includes a first solvent and a secondsolvent, a boiling point of the first solvent is 80° C. or more and lessthan a crystallization temperature of the sulfide solid electrolyte, thefirst solvent is acyclic ether based solvent, acyclic ester basedsolvent, or acyclic ketone based solvent, a boiling point of the secondsolvent is a crystallization temperature of the sulfide solidelectrolyte or more, and a content proportion of the first solvent inthe solid electrolyte-containing layer is 0.01 weight % or more.

C. Method for Producing all Solid State Battery

The method for producing an all solid state battery in the presentdisclosure comprises a coating step of forming a coating layer bycoating a substrate with the above described slurry, a drying step offorming a dried coating layer by drying the coating layer, and apressing step of forming a solid electrolyte-containing layer bypressing the dried coating layer, and a drying condition in the dryingstep is adjusted so as a content proportion of the first solvent in thesolid electrolyte-containing layer is 0.01 weight % or more.

According to the present disclosure, by adjusting the drying conditionin the drying step so as the solid electrolyte-containing layer includesa predetermined amount of a specific solvent, an all solid state batterywith low ion resistivity may be obtained.

FIG. 2 is a flowchart illustrating a part of a method for producing anall solid state battery in the present disclosure. First, in FIG. 2, asulfide solid electrolyte, a first solvent, and a second solvent areprepared, and a slurry is prepared by mixing and kneading these. Next, asubstrate is coated with the obtained slurry to form a coating layer(coating step). Then, the obtained coating layer is dried to form adried coating layer (drying step). Then, the obtained dried coatinglayer is pressed to form a solid electrolyte-containing layer (pressingstep). By adjusting the drying condition in the drying step so as acontent proportion of the first solvent in the solidelectrolyte-containing layer is 0.01 weight % or more, a solidelectrolyte-containing layer with low ion resistivity may be obtained,and as the result, an all solid state battery with low ion resistivitymay be obtained.

1. Coating Step

The coating step in the present disclosure is a step of forming acoating layer by coating a substrate with the above described slurry.The slurry may be in the same contents as those described in “A. Slurry”above; thus, the descriptions herein are omitted.

The substrate is not particularly limited, and may be appropriatelyselected according to the kind of the solid electrolyte-containinglayer. For example, when the solid electrolyte-containing layer is acathode active material layer, a cathode current collector or a solidelectrolyte layer, for example, may be used as the substrate. Similarly,when the solid electrolyte-containing layer is an anode active materiallayer, an anode current collector or a solid electrolyte layer, forexample, may be used as the substrate. Meanwhile, when the solidelectrolyte-containing layer is a solid electrolyte layer, a cathodeactive material layer or an anode active material layer, for example,may be used as the substrate. Also, regardless of the kind of the solidelectrolyte-containing layer, the slurry may be coated on a peelablesubstrate. Examples of the peelable substrate may include a metal sheet,and a resin sheet such as a fluorine based resin sheet.

Examples of a method for coating the slurry may include methods commonlyused in the art, such as a doctor blade method, a die coating method, agravure coating method, a spray coating method, an electrostatic coatingmethod and a bar coating method.

2. Drying Step

The drying step in the present disclosure is a step of forming a driedcoating layer by drying the coating layer. Further, in the presentdisclosure, the drying condition in the drying step is adjusted so as acontent proportion of the first solvent in the solidelectrolyte-containing layer is 0.01 weight % or more.

The drying temperature is not particularly limited, and, in embodiments,may be a temperature less than the crystallization temperature of thesulfide solid electrolyte contained in the coating layer. The reasontherefor is to prevent the deterioration of the sulfide solidelectrolyte. The heating temperature may be the temperature lower thanthe crystallization temperature of the sulfide solid electrolyte by 5°C. or more, and may be the temperature lower by 10° C. or more. Thedrying temperature is, for example, 60° C. or more, may be 80° C. ormore, and may be 100° C. or more. Meanwhile, the drying temperature is,for example, 190° C. or less, may be 170° C. or less, and may be 160° C.or less.

Examples of the method for drying the coating layer may include generalmethods such as warm-air/hot-blast drying, infrared ray drying,reduced-pressure drying, and dielectric heat drying. Examples of thedrying atmosphere may include inert gas atmospheres such as an Ar gasatmosphere and a nitrogen gas atmosphere. Also, the drying may becarried out under an atmospheric pressure, and may be under a reducedpressure.

Also, the drying condition in the drying step is adjusted so as acontent proportion of the first solvent in the solidelectrolyte-containing layer after the pressing step is 0.01 weight % ormore. In the drying step, the drying conditions may be adjusted so as toobtain the solid electrolyte-containing layer described in “B. All solidstate battery” above.

3. Pressing Step

The pressing step in the present disclosure is a step of forming a solidelectrolyte-containing layer by pressing the dried coating layer.

Examples of the method for pressing the dried coating layer may includea roll press and a plate press. The linear pressure applied at the timeof the roll press is, for example, 1.5 t/cm or more, and may be 2 t/cmor more. Meanwhile, the linear pressure at the time of the roll pressis, for example, 10 t/cm or less.

Also, the surface pressure applied at the time of the plate press is,for example, 800 MPa or more, may be 1000 MPa or more, and may be 1200MPa or more. Meanwhile, the surface pressure applied at the time of theplate press is, for example, 3000 MPa or less.

The pressing time is not particularly limited. Also, in the pressingstep, the dried coating layer may be heated simultaneously with thepressing.

4. Others

In the method for producing an all solid state battery in the presentdisclosure, the solid electrolyte-containing layer may be obtained byeach above described step. That is, the method for producing an allsolid state battery includes a solid electrolyte-containing layerforming step containing each above described step.

Meanwhile, the method for producing an all solid state battery usuallycomprise a cathode active material layer forming step of forming acathode active material layer, a solid electrolyte layer forming step offorming a solid electrolyte layer, and an anode active material layerforming step of forming an anode active material layer. That is, in themethod for producing an all solid state battery in the presentdisclosure, at least one of the cathode active material layer formingstep, the solid electrolyte layer forming step, and the anode activematerial layer forming step is the solid electrolyte-containing layerforming step.

Also, the all solid state battery obtained by each above described stepmay be in the same contents as those described in “B. All solid statebattery” above; thus, the descriptions herein are omitted.

Further, the present disclosure may also provide a method for producinga solid electrolyte-containing layer used for an all solid statebattery, the method comprising: a coating step of forming a coatinglayer by coating a substrate with the above described slurry, a dryingstep of forming a dried coating layer by drying the coating layer, and apressing step of forming the solid electrolyte-containing layer bypressing the dried coating layer, and a drying condition in the dryingstep is adjusted so as a content proportion of the first solvent in thesolid electrolyte-containing layer is 0.01 weight % or more.

Further, the present disclosure may also provide a method for producinga solid electrolyte-containing layer used for an all solid statebattery, the method comprising: a filling step of forming a second layerby filling a solvent including at least one of a first solvent and asecond solvent, onto a first layer including a sulfide solidelectrolyte, and a pressing step of forming the solidelectrolyte-containing layer by pressing the second layer, and a contentproportion of the solvent in the solid electrolyte-containing layer isadjusted so as to be 0.01 weight % or more.

EXAMPLES Example 1

<Production of Cathode Active Material Layer>

LiNi_(1/3)Mn_(1/3)Co_(1/3)O₂ (manufactured by Nichia Corporation) as acathode active material and LiI—Li₂O—Li₂S—P₂S₅ as a sulfide solidelectrolyte were weighed and mixed so as to be cathode activematerial:sulfide solid electrolyte=75:25 in the weight ratio. To 93.5weight parts of the obtained mixture, a PVDF binder solution was addedso as the solid content of the solution was 3.0 weight parts, and 3.0weight parts of VGCF (a conductive material, manufactured by Showa DenkoK. K.) and an ethylcellulose solution (thickening agent, manufactured byNacalai Tesque, Inc.) were added so as the solid content of the solutionwas 0.2 weight parts. Further, as the second solvent, 0.3 weight partsof acetophenone was added, thereby obtained a composition of total of100 weight parts. A cathode slurry was prepared by adding 66.7 weightparts of methyl isobutyl ketone (dehydrated product) as the firstsolvent to the obtained composition, and carrying out an ultrasonictreatment for 60 seconds with an ultrasonic homogenizer (UH-50,manufactured by SMT Co., Ltd.). A cathode current collector (an Al foil)was coated with this cathode slurry using a baker applicator, driednaturally for 5 minutes, and dried by hot air at 100° C. Thereby, acathode including a cathode current collector and a cathode activematerial layer was obtained.

<Production of Anode Active Material Layer>

Natural graphite as an anode active material and LiI—Li₂O—Li₂S—P₂S₅ as asulfide solid electrolyte were weighed and mixed so as to be anodeactive material:sulfide solid electrolyte=60:40 in the weight ratio. To96.5 weight parts of the obtained mixture, a PVDF binder solution wasadded so as the solid content of the solution was 3.0 weight parts andan ethylcellulose solution (thickening agent, manufactured by NacalaiTesque, Inc.) was added so as the solid content of the solution was 0.2weight parts. Further, as the second solvent, 0.3 weight parts ofacetophenone was added, thereby obtained a composition of total of 100weight parts. An anode slurry was prepared by adding 80 weight parts ofmethyl isobutyl ketone (dehydrated product) as the first solvent to theobtained composition, and carrying out an ultrasonic treatment for 60seconds with an ultrasonic homogenizer (UH-50, manufactured by SMT Co.,Ltd.). An anode current collector (a SUS foil) was coated with thisanode slurry using a baker applicator, dried naturally for 5 minutes,and dried by hot air at 100° C. Thereby, an anode including an anodecurrent collector and an anode active material layer was obtained.

<Production of Solid Electrolyte Layer>

To 96.2 weight parts of a sulfide solid electrolyte LiI—Li₂O—Li₂S—P₂S₅,a PVDF binder solution was added so as the solid content of the solutionwas 3.0 weight parts, and an ethylcellulose solution (thickening agent,manufactured by Nacalai Tesque, Inc.) was added so as the solid contentof the solution was 0.5 weight parts. Further, as the second solvent,0.3 weight parts of acetophenone was added, thereby obtained acomposition of total of 100 weight parts. A slurry for a solidelectrolyte layer was prepared by adding 122.2 weight parts of methylisobutyl ketone (dehydrated product) as the first solvent to theobtained composition, and carrying out an ultrasonic treatment forseconds with an ultrasonic homogenizer (UH-50, manufactured by SMT Co.,Ltd.). A substrate (an Al foil) was coated with this slurry for a solidelectrolyte layer by using a baker applicator, dried naturally for 5minutes, and dried by hot air at 100° C. Thereby, a substrate and asolid electrolyte layer were obtained.

<Production of all Solid State Battery>

The solid electrolyte layer peeled off from the substrate was insertedinto a ceramic mold (cross-sectional area of 1.0 cm²) in an inert gas,the cathode active material layer was placed on one surface, and theanode active material layer was placed on other side surface. Theobtained stack was pressed under pressure of 4.3 ton at the scale of ahydraulic press, and confined under 1 MPa. Thereby, an all solid statebattery was obtained. All of the cathode active material layer, thesolid electrolyte layer, and the anode active material layer of theobtained all solid state battery correspond to the solidelectrolyte-containing layer.

Examples 2 to 5

An all solid state battery was obtained in the same manner as in Example1 except that the proportion of the second solvent (acetophenone) andthe treatment time of the hot-air drying were appropriately adjusted inthe manufacture of the cathode active material layer, the solidelectrolyte layer, and the anode active material layer.

Example 6

An all solid state battery was obtained in the same manner as in Example1 except that LiPF₆ was added as a metal salt to the second solvent,acetophenone, so as the concentration was 1.0 mol/l, in the manufactureof the cathode active material layer, the solid electrolyte layer, andthe anode active material layer.

Example 7

An all solid state battery was obtained in the same manner as in Example1 except that an infrared drying treatment was carried out so as thelayer surface was 150° C., instead of the hot-air drying at 100° C., inthe manufacture of the cathode active material layer, the solidelectrolyte layer, and the anode active material layer.

Example 8

An all solid state battery was obtained in the same manner as in Example1 except that methyl isobutyl ketone was changed to butyl butyrate, andacetophenone was changed to 3-hydroxy-2,2,4-trimethylpentyl isobutyrate,in the manufacture of the cathode active material layer, the solidelectrolyte layer, and the anode active material layer.

Example 9

An all solid state battery was obtained in the same manner as in Example1 except that methyl isobutyl ketone was changed to diethylene glycoldiethyl ether, and acetophenone was changed to triethylene glycolmonomethyl ether, in the manufacture of the cathode active materiallayer, the solid electrolyte layer, and the anode active material layer.

Example 10

An all solid state battery was obtained in the same manner as in Example1 except that methyl isobutyl ketone was changed to diisobutyl ketone,and acetophenone was changed to decaethylene glycol monomethyl ether, inthe manufacture of the cathode active material layer, the solidelectrolyte layer, and the anode active material layer.

Example 11

An all solid state battery was obtained in the same manner as in Example1 except that methyl isobutyl ketone was changed to diisobutyl ketone,and acetophenone was changed to polyethylene glycol monolaurate (10 E.O.), in the manufacture of the cathode active material layer, the solidelectrolyte layer, and the anode active material layer.

Comparative Example 1

In the manufacture of the cathode active material layer, the solidelectrolyte layer, and the anode active material layer, each of thecathode active material layer, the solid electrolyte layer, and theanode active material layer was manufactured by not using the solvents(methyl isobutyl ketone and acetophenone), but by powder mixing andpowder compacting the materials other than the solvents in a mortar for10 minutes. An all solid state battery was obtained in the same manneras in Example 1 except that these layers were used.

Comparative Example 2

An all solid state battery was obtained in the same manner as in Example1 except that the second solvent (acetophenone) was not used, and thetreatment time of the hot-air drying was appropriately adjusted in themanufacture of the cathode active material layer, the solid electrolytelayer, and the anode active material layer.

Comparative Example 3

An all solid state battery was obtained in the same manner as in Example1 except that the second solvent (acetophenone) was not used, and methylisobutyl ketone was changed to tetrahydrofuran in the manufacture of thecathode active material layer, the solid electrolyte layer, and theanode active material layer.

<Measurement of Remaining Solvent Amount>

The remaining solvent amount of the cathode active material layer, thesolid electrolyte layer, and the anode active material layer obtained inExamples 1 to 11 and Comparative Examples 1 to 3 was measured with a gaschromatography (GC). As for the measuring method, the measuring of theremaining solvent amount was carried out with a headspace GC. As for thedevice constitution, a headspace sampler 7697A Type from AgilentTechnologies was used for a sampler part, and 7890B GC from AgilentTechnologies was used for a GC analyzer part. The measuring conditionsare shown below.

(Analyzing Conditions)

Column: DB-Select 624UI

Inlet temperature: 150° C. Carrier gas: helium

FID: 250° C.

MS mode: Scan (m/z: 29-250)

The remaining solvent amount in the cathode active material layer isshown in Table 1. Incidentally, the results of the remaining solventamount in the solid electrolyte layer and the anode active materiallayer were similar to that of the cathode active material layer.

<Measurement of Ion Resistivity>

The Li ion conductivity (ambient temperature) measurement was carriedout by an AC impedance method to the all solid state batteries obtainedin Examples 1 to 11 and Comparative Examples 1 to 3 so as to evaluatethe ion resistivity. Solartron (SI1260) from Toyo Corporation was usedfor measuring, and the measuring conditions for the impedancemeasurement were; applied voltage of 10 mV, measuring frequency range of0.01 MHz to 1 MHz at 25° C. (adjusted in a constant temperature bath).Incidentally, a test cell was prepared by the following method. Atfirst, in an environment of 25° C.±4° C., a not yet charged all solidstate battery was charged at constant current with current value of 0.1C until the voltage of a terminal per an all solid state battery reachesthe predetermined voltage, and then, the all solid state battery wascharged at constant current/constant voltage for one hour, maintainingthe voltage at the predetermined voltage. After the initial charge, theall solid state battery was discharged at constant current/constantvoltage for 10 hours to 3.0 V at 0.2 C. After that, in an environment of25° C.±4° C., the all solid state battery was charged at constantcurrent to 4.0 V at current value of 0.2 C. Thereby, a test cell formeasuring the Li ion conductivity was prepared. The ion resistivity wasdetermined as the reciprocal of the obtained lithium ion conductivity.The results are shown in Table 1.

<Measurement of Filling Rate>

The cathode active material layer, the solid electrolyte layer, and theanode active material layer obtained in Examples 1 to 11 and ComparativeExamples 1 to were subjected to a pressing treatment with a rollpressing device under line pressure of 4 t/m, and the filling rate afterpressing was calculated. The results are shown in Table 2.

TABLE 1 First solvent Second solvent Remaining solvent Boiling Boilingamount (weight %) Ion Kind of point Kind of point First Secondresistivity solvent (° C.) solvent (° C.) solvent solvent Total (%)Example 1 A1 116 B1 202 0.2 0.3 0.5 4.1 Example 2 0.2 0.05 0.25 5.3Example 3 0.01 0.3 0.31 4.8 Example 4 0.01 2.99 3 3.4 Example 5 0.2 44.2 11.0 Example 6 0.2 0.3 0.5 5.1 Example 7 0.2 0.3 0.5 4.8 Example 8A2 165 B2 253 0.2 0.3 0.5 4.3 Example 9 A3 162 B3 249 0.2 0.3 0.5 4.0Example 10 A4 168 B4 >250 0.2 0.3 0.5 3.8 Example 11 B5 >250 0.2 0.3 0.53.6 Comp. Ex. 1 — — — — — — — 18.1 Comp. Ex. 2 A1 116 — — 0.005 — 0.00519.8 Comp. Ex. 3 C1  65 — — 0.2 — 0.2 25.1 A1: methyl isobutyl ketoneA2: butyl butyrate A3: diethylene glycol diethyl ether A4: diisobutylketone B1: acetophenone B2: 3-hydroxy-2,2,4-trimethylpentyl isobutyrateB3: triethylene glycol monomethyl ether B4: decaethylene glycolmonomethyl ether B5: polyethylene glycol monolaurate (10 E. O.) C1:tetrahydrofuran

TABLE 2 Filling rate (%) First solvent Second solvent Cathode AnodeBoiling Boiling active active Solid Kind of point Kind of point materialmaterial Electrolyte solvent (° C.) solvent (° C.) layer layer layerExample 1 A1 116 B1 202 97.1 97.9 96.1 Example 2 96.0 96.6 95.0 Example3 96.1 96.4 95.7 Example 4 99.1 99.8 98.9 Example 5 — — — Example 6 96.997.1 96.7 Example 7 96.9 96.9 96.6 Example 8 A2 165 B2 253 97.5 97.396.8 Example 9 A3 162 B3 249 98.0 98.3 97.6 Example 10 A4 168 B4 >25098.9 99.8 98.2 Example 11 B5 >250 99.0 99.7 98.6 Comp. Ex. 1 — — — —88.1 88.7 87.6 Comp. Ex. 2 A1 116 — — — — — Comp. Ex. 3 C1  65 — — 93.894.7 93.4

As shown in Table 1, compared to Comparative Example 1 wherein the firstsolvent and the second solvent were not included, it was able todecrease the ion resistivity in Examples 1 to 11, by the first solventand the second solvent being included in the solidelectrolyte-containing layer including the sulfide solid electrolyte. Itis presumed that, since the first solvent and the second solvent wereleft remained in the all solid state battery, the interface resistance(friction resistance) between the particles included in the electrodelayer was decreased during the press so that the sliding property on theparticle interface was improved. Specifically, as shown in Table 2, itis presumed that, since the sliding property at particle interface wasimproved, the filling rate after pressing was improved, and the ion pathwas formed effectively so that the ion resistivity was decreased.

Also, comparing Example 1 and Example 6, the ion resistivity in Example1, wherein the metal salt LiPF₆ was not added, was lower than the ionresistivity in Example 6, wherein the metal salt LiPF₆ was added. Thereason is presumed that a part of the sulfide solid electrolyte wasdeteriorated by the metal salt so that the interface resistance wasincreased.

Also, when the remaining solvent amount was lower than 0.01 weight % asComparative Example 2, the ion resistivity was increased. The reasontherefor is presumed that, since the remaining solvent amount was low,the solid content was agglutinated so that the improving effect of thesliding property on the particle interface was not obtained. Further,when tetrahydrofuran was used as the first solvent as in ComparativeExample 3, the ion resistivity was remarkably increased. The reasontherefor is presumed that a cyclic organic solvent such astetrahydrofuran easily dissolves and deteriorates the sulfide solidelectrolyte. Also, the reason therefor is presumed that tetrahydrofuranformed a peroxide with an oxygen in the air.

REFERENCE SIGNS LIST

-   1 . . . cathode active material layer-   2 . . . anode active material layer-   3 . . . solid electrolyte layer-   10 . . . all solid state battery

What is claimed is:
 1. A slurry comprising a sulfide solid electrolyteand a solvent, and the solvent includes a first solvent and a secondsolvent, a boiling point of the first solvent is 80° C. or more and lessthan a crystallization temperature of the sulfide solid electrolyte, thefirst solvent is acyclic ether based solvent, acyclic ester basedsolvent, or acyclic ketone based solvent, and a boiling point of thesecond solvent is the crystallization temperature of the sulfide solidelectrolyte or more.
 2. The slurry according to claim 1, wherein theboiling point of the first solvent is less than 200° C.
 3. The slurryaccording to claim 1, wherein the boiling point of the second solvent is200° C. or more.
 4. A slurry comprising a sulfide solid electrolyte anda solvent, and the solvent includes a first solvent and a secondsolvent, a boiling point of the first solvent is 80° C. or more and lessthan 200° C., and the first solvent is acyclic ether based solvent,acyclic ester based solvent, or acyclic ketone based solvent, and aboiling point of the second solvent is 200° C. or more.
 5. The slurryaccording to claim 1, wherein a proportion of the second solvent to 100weight parts of solid content of the slurry is 0.05 weight parts ormore.
 6. The slurry according to claim 1, further comprising a binder.7. The slurry according to claim 1, further comprising an activematerial.
 8. An all solid state battery comprising a cathode activematerial layer, a solid electrolyte layer, and an anode active materiallayer, and at least one layer of the cathode active material layer, thesolid electrolyte layer, and the anode active material layer is a solidelectrolyte-containing layer including a sulfide solid electrolyte, thesolid electrolyte-containing layer includes a first solvent and a secondsolvent as solvents, a boiling point of the first solvent is 80° C. ormore and less than a crystallization temperature of the sulfide solidelectrolyte, the first solvent is acyclic ether based solvent, acyclicester based solvent, or acyclic ketone based solvent, a boiling point ofthe second solvent is a crystallization temperature of the sulfide solidelectrolyte or more, and a content proportion of the first solvent inthe solid electrolyte-containing layer is 0.01 weight % or more.
 9. Theall solid state battery according to claim 8, wherein a contentproportion of the second solvent in the solid electrolyte-containinglayer is 0.05 weight % or more.
 10. The all solid state batteryaccording to claim 8, wherein a content proportion of the solvents inthe solid electrolyte-containing layer is 0.25 weight % or more.
 11. Amethod for producing an all solid state battery, the method comprising:a coating step of forming a coating layer by coating a substrate withthe slurry according to claim 1, a drying step of forming a driedcoating layer by drying the coating layer, and a pressing step offorming a solid electrolyte-containing layer by pressing the driedcoating layer, and a drying condition in the drying step is adjusted soas a content proportion of the first solvent in the solidelectrolyte-containing layer is 0.01 weight % or more.